Silicon carbide (SiC) photodiodes such as disclosed in commonly assigned Brown et al., U.S. Pat. No. 5,394,005, have high optical responsivity in the ultra-violet region. It would be desirable to use SiC photodiodes in detector circuits, however, the photon flux impinging on a gas turbine optical flame detector port is very small (i.e., on the order of 1.times.10.sup.9 per second per square centimeter), especially during start up procedures, when the primary flame is at a low intensity level.